This circuit uses a transistor as a sensor and operates in the range of 0 to 50º C. We found it in old documentation. Operational equivalents can be used.
With this circuit it is possible to obtain an input resistance of 100Gohms for a multimeter, with...
This amplifier, to detect biological signals in implanted transmitters, uses transistors such as...
This application is not modern since few computers have parallel ports. But you can use this...